Update IP in model after changing VRRP IP address.

Model is now updated after changing VRRP IP address (if changed correctly)
This way, model and router configuration are sync, and the GUI shows currently configured IP address.
Merge pull request #547 from isartcanyameres/fix/update-vrrp-model-after-change-vrrp-ip

Update IP in model after changing VRRP IP address.